Summary of the Invention
The invention is based on the object of further developing a suspension eye of the type described at the beginning in such a way that, with small rebound movements, a relatively soft suspension is achieved with good vibration insulating effect, while in the range of larger deflections a greater progressivity of the characteristic is attained, that is the springing becomes considerably harder, until ultimately the maximum spring excursion is reached.
This is achieved according to the invention by the liner consisting of extensible, resiliently compliant material, two bushes being embedded in the band, and the liner arranged in the band bearing directly against the bushes. What is essential is that the liner no longer consists of tension-resistant material which is elastically deformable merely in the plane of the band, but that extensible, resiliently compliant, that is inherently elastic material is also used for the liner. This other material allows that the liner is not, as previously, subjected to bending stress - apart from its stop function - but that, with small rebounds, the liner also remains free from appreciable bending forces, so that, in the range of these small deflections, the properties of the band of elastomer material alone come into use. This springing is consequently particularly soft in this initial range and thus sound-insulating and vibration-insulating. Although the liner is provided alongside the band from the outset, its action in terms of force does not commence virtually until the transition range between small and large rebounds, i.e. the liner creates a free space in terms of force for small rebound movements, in which it does not or virtually does not come into effect. Instead, its action in terms of force commences at the transition point to large rebounds, so that the spring characteristic receives in this range as it were a transition kink, from whence a significantly increased progressivity is produced. It is important to appreciate that, at this instant of transition, the spring excursion is not already limited by a mechanically acting stop but that now, upon extension of the liner, in fact for the first time the progressive part of the spring characteristic occurs. In this range, the springing is thus very hard and, with ever increasing rebounds, opposes considerable restoring forces. During this, the liner is lengthened and extended out of the stretched position. The material of the liner thus itself has an appreciable spring excursion and also has a considerable recovery, so that no solid stop is formed in this range. A solid stop is, at it were, dispensed with in the case of the new suspension eye, which is possible due to the strong progressivity. The band and the liner are in this case designed and dimensioned such that the maximum operating load between the suspension points, and consequently the permissible tensile stress in the material, are not exceeded. Also important is the arrangement of the bushes in the band, to be precise in two respects. Firstly, these bushes form stress-appropriate receiving points for receiving pin-shaped hooks on the floor of the motor vehicle on the one hand and on the exhaust system on the other hand, to be precise without there being the risk that the band of elastic material is torn or otherwise damaged by the attachment of these pin-shaped hooks. Secondly, these bushes serve as direct application of force for the liner in the range of relatively large rebounds. Regions of elastomer material which could thereby be subjected to excessive compressive stresses are avoided.
The liner may consist of an, in particular, multi-layered loop of yarn, that is of a yarn which is looped several times around the suspension points on the bushes. This has the effect, as it were, of forming a yarn loop assembly, which can be made on the one hand sufficiently compliantly elastic and on the other hand correspondingly reinforcing.
The band and the liner may have spring excursions of a similar order of magnitude. Consequently, a clear delimitation from a tension-resistant liner is achieved, which has virtually no appreciable spring excursion. Due to the fact that the spring excursions are approximately of the same order of magnitude, the spring characteristic receives two regions which are distinctly and tendentially separate from each other and joined by a transition region. In the lower region, the characteristic has a small slope and in the upper region it has a large slope.
The loop of yarn may consist of a resiliently compliantly made yarn of natural materials such as cotton, silk or the like and/or of plastic. All that is important is that the yarn must be finished such that it itself becomes resiliently compliant.
The suspension eye is expediently designed as an injection molding and has inserted crude elastomer workpieces surrounded by injection molding material. These crude elastomer pieces serve to fix the rhombus-like initial shape of the liner in the unloaded position.
A process for producing a suspension eye having two suspension points uses an injection mold and is defined according to the invention by two bushes being introduced in stable position into the injection mold, the liner being placed over the bushes and spread out into the rhombus-like initial shape by at least one crude elastomer piece likewise to be inserted into the injection mold, and elastomer material being injected round the inserted parts. Although the material of the liner is in itself not very dimensionally stable, the rhombus-like initial shape is secured and achieved by the liner being spread out or set out correspondingly between the bushes and an inserted crude elastomer piece before the injection of the remaining elastomer material into the injection mold takes place. It goes without saying that a vulcanization in the mold subsequently follows, if, for example, rubber is used as elastomer material.
In addition, side cover parts of crude elastomer material may be inserted into the injection mold in order that, when it is introduced into the injection mold, the liner is not spread out only in the direction of the plane of the suspension eye but is also held and mounted in the direction perpendicular thereto. The liner is consequently given is symmetrical seating within the band.